Clearly, we didn't see her at her best today, for a variety of reasons, and it would be unfair to judge her on that effort, just as it would be to judge Frankel on last year's Royal Ascot performance.
The comparison between Black Caviar and Dayjur is an interesting one.
Physically, it's no contest, with the mare being a magnificent specimen of tremendous power, whereas Dayjur was rather more racing-like.
As for performance, this is where it gets more difficult! Dayjur won some of his races more brilliantly, a la Frankel, whereas Black Caviar tends to race less exuberantly, winning cosily, hand-ridden, and they like her to be ridden that way. That has probably helped to prolong her career. Dayjur managed to get himself beaten by a nonentity (Tod) as a 3-y-o (we can forgive his other defeats) but Black Caviar has been able to remain unbeaten. Also, Black Caviar has won more Group 1s than Dayjur (12-3), although it was hardly his fault that he was retired after his Belmont run.
The thing that really sways it for me is that Hay List, who she's thrashed every time she's met him, is a better sprinter than any of the horses Dayjur beat. Remember, Hay List would be hailed as one of the greats if Black Caviar hadn't been born - he's got a higher rating than Takeover Target, Choisir and Scenic Blast, who were all top-notch Group 1 horses.
So, the nod goes to Black Caviar, but both are great horses, a privilege to see them race.